Method for encoding and decoding images, and device using same

1. A method for inter prediction, comprising:

receiving, by a decoding apparatus, mode information on an inter prediction of a current block, wherein the mode information includes merge flag information indicating whether an inter prediction mode for the current block is a merge mode;

deriving, by the decoding apparatus, merge candidates of the current block based on neighboring blocks of the current block;

selecting, by the decoding apparatus, a merge candidate from the derived merge candidates;

deriving, by the decoding apparatus, a motion vector of the current block as to be equal to a motion vector of the selected merge candidate; and

generating, by the decoding apparatus, a prediction sample of the current block based on the motion vector of the current block,

wherein the neighboring blocks includes a left neighboring block, an upper neighboring block, an upper-right corner neighboring block, an upper-left corner neighboring block, and a lower-left corner neighboring block of the current block.

2. The method of claim 1 , wherein the mode information includes residual flag information indicating whether there is a residual signal for the current block, and wherein the residual flag information is received prior to the merge flag information.

3. The method of claim 2 , wherein the merge candidates has the same configuration regardless whether there is the residual signal for the current block.

4. The method of claim 2 , wherein the derived motion vector is one of L 0 motion vector for forward prediction, L 1 motion vector for backward prediction, and Bi motion vector for bi prediction.

5. The method of claim 2 , wherein the left neighboring block is a bottom-most block among left neighboring blocks adjacent to the left boundary of the current block, and the top neighboring block is a right-most block among upper neighboring blocks adjacent to the upper boundary of the current block.

6. The method of claim 1 , wherein the neighboring blocks further includes a co-located block which is a block at the same position as the current block among blocks in a reference picture.

7. The method of claim 2 , wherein decoding the received mode information comprises:

decoding the merge flag information prior to the residual flag information; and

decoding the residual flag information only when the decoded merge flag information indicates that the inter prediction mode for the current block is the merge mode.

8. A decoding apparatus for decoding video, comprising:

an entropy decoder configured to receive mode information on an inter prediction of a current block, wherein the mode information includes merge flag information indicating whether an inter prediction mode for the current block is a merge mode;

a predictor configured to derive merge candidates of the current block based on neighboring blocks of the current block, to select a merge candidate from the derived merge candidates, to derive a motion vector of the current block as to be equal to a motion vector of the selected merge candidate, and to generate a prediction sample of the current block based on the motion vector of the current block,

wherein the neighboring blocks includes a left neighboring block, an upper neighboring block, an upper-right corner neighboring block, an upper-left corner neighboring block, and a lower-left corner neighboring block of the current block.

9. The apparatus of claim 8 , wherein the mode information includes residual flag information indicating whether there is a residual signal for the current block, and

wherein the residual flag information is received prior to the merge flag information.

10. The apparatus of claim 9 , wherein the merge candidates has the same configuration regardless whether there is the residual signal for the current block.

11. The apparatus of claim 9 , wherein the derived motion vector is one of L 0 motion vector for forward prediction, L 1 motion vector for backward prediction, and Bi motion vector for bi prediction.

12. The apparatus of claim 9 , wherein the left neighboring block is a bottom-most block among left neighboring blocks adjacent to the left boundary of the current block, and the top neighboring block is a right-most block among upper neighboring blocks adjacent to the upper boundary of the current block.

13. The apparatus of claim 8 , wherein the neighboring blocks further includes a co-located block which is a block at the same position as the current block among blocks in a reference picture.

14. The apparatus of claim 9 , wherein an entropy decoder decodes the received mode information:

wherein the merge flag information is decoded prior to the residual flag information; and

wherein the residual flag information is decoded only when the decoded merge flag information indicates that the inter prediction mode for the current block is the merge mode.